Method for producing a metallic core for use in cylinder sleeves for an electrophotographic process

ABSTRACT

An improved method for producing a metallic core for use in the production of a blanket cylinder or an image cylinder sleeve for use in electophotographic processes. The sleeves includes aluminum or other suitable metal, which is rendered more suitable for use as a sleeve surface by oxidation.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. Ser. No. 10/903,340 filed Jul.30, 2004.

FIELD OF THE MENTION

This invention relates to an improved method for producing a metalliccore for use in the production of a blanket cylinder or an imagecylinder sleeve for use in electrophotographic processes. The sleevesinclude a core of aluminum or other suitable metal, which is renderedmore suitable for use as a sleeve surface by oxidation.

BACKGROUND OF THE INVENTION

In electrophotographic processes requiring an image cylinder and ablanket cylinder to produce electrophotographic copies, the imagecylinder typically receives a charge, an image and a toner coating onthe image area and then transfers the toner image to a blanket cylinder.The blanket cylinder transfers the toner image to a substrate, such aspaper or the like, which passes via a web between the blanket cylinderand a back pressure roller to transfer the toner image to the substratewith the substrate thereafter being fused, as well known to the art.

In such processes, the image cylinder has a cylinder that typicallyincludes a mandrel that may be of aluminum, steel or any other suitableand durable metal or conductive plastic of a suitable thickness toproduce a non-compliant member that may be about 10 millimeters (mm) inthickness. The mandrel may include reinforcing structure internally andincludes a very smooth, low out-of-round tolerance exterior.

The image cylinder includes a mandrel and a sleeve positioned over theoutside of the mandrel and is used for production and transfer of theimages to the blanket cylinder. The mandrel also includes bearingsconnected to each of its ends for positioning in an electophotographicmachine and has an air inlet into an interior of the mandrel for an airdischarge to a plurality of holes placed around one end of the mandrelnear a tapered end of the mandrel.

The blanket cylinder has a cylinder that typically includes a mandrelthat may be of aluminum, steel or any other suitably durable metal orconductive plastic of a suitable thickness to produce a non-compliantmember that may be about 10 mm in thickness. The blanket cylinderincludes a mandrel and a sleeve positioned over the outside of themandrel and is used for transfer of images from the blanket cylinder toa substrate.

The mandrel may include reinforcing structure internally and includes avery smooth, low out-of-round tolerance exterior. The mandrel alsoincludes bearings connected to each of its ends for positioning in anelectrophotographic copying machine and has an air inlet into aninterior of the mandrel for an air discharge through a plurality ofholes placed around one end of the mandrel near a tapered end of themandrel.

The sleeves have been produced by the use of a metal core, which istypically a non-compliant metal member, such as aluminum, nickel, or thelike, that may be produced by plating, extrusion or the like.

The production of metal cores by plating or the like has been found tobe expensive and difficult to control sufficiently to produce a metalcore of uniform thickness without nodules, voids or the like. Whiledesirable cores have been produced in this manner, it is expensive anddifficult to dependably produce high quality metal cores. In analternate process, extrudates such as aluminum may be used. Suchextrudates have a relatively constant internal diameter but the surfaceis relatively uneven for the purposes for which the metal cores areused. It has been found that such aluminum extrudates can be placed on amandrel with an interference fit and machined to have a desired outsidediameter and finish.

It has also been found, in the use of such cores, that if scratches orother defects occur on the core inside diameter during mounting or whileon the mandrel it renders the installation and demounting of the mandrelwith an interference fit by the air step method to be very difficult ifnot impossible. Further, such variations can result in difficulty inproducing an exterior surface of the desired diameter and finish. It hasalso been found that when the core is placed on a mandrel with aninterference fit in many instances the metal, such as aluminum, tends togall, i.e., suffer extensive abrasive wear and deposit quantities of theinner surface of the aluminum extrudate on the exterior of the mandrel.Both of these events are very undesirable and result in a loss oftolerance control both on the exterior of the mandrel and the inside ofthe extrudate. Even if the outside of the extrudate as mounted on themandrel has been machined to the desired diameter and tolerance, theloss of metal to the surface of the mandrel may result in anunacceptable variation in the outer diameter when the core produced fromthe extrudate is placed on another mandrel.

Since the use of metal extrudates allows the production of metal coresfor the blanket cylinder and image cylinder sleeves much moreeconomically, a method has been sought by which these difficulties andothers can be obviated and metal cores having the desired toleranceproduced more dependably from aluminum extrudates.

SUMMARY OF THE INVENTION

According to the present invention, such desirable cores are produced bya method for producing a metallic core having an oxidized inner surfaceand an oxidized outer surface for use in a blanket cylinder or an imagecylinder for use in an electrophotographic process, the methodcomprising: producing a metallic tube having an inner diameter, an innersurface, an outer surface and an outer diameter, the inner diameterbeing smaller than the outer diameter of a mandrel so that the metallictube can be mounted with an interference fit over the outer diameter ofthe mandrel; oxidizing the inner surface of the metallic tube to producea metallic oxide layer on the inner surface of the metallic tube;positioning the oxidized inner surface metallic tube on a mandrel withan interference fit and machining an outer surface of the oxidized innersurface metallic tube to a desired diameter and finish; and, oxidizingthe outer surface of the oxidized inner surface metallic tube to producethe metallic core having an oxidized inner surface metallic core havingan oxidized inner surface and an oxidized outer surface of the oxidizedinner surface.

Suitable extrudates are also produced by a method for producing analuminum core having an oxidized inner surface and an oxidized outersurface for use in a blanket cylinder or an image cylinder for use in anelectrophotographic process, the method comprising: producing analuminum tube having an inner diameter, an inner surface, an outersurface and an outer diameter, the inner diameter being smaller than anouter diameter of a mandrel so that the aluminum tube can be mountedwith an interference fit over the outer diameter of the mandrel;oxidizing the inner surface of the aluminum tube to produce an aluminumoxide layer on the inner surface of the aluminum tube; positioning theoxidized inner surface aluminum tube on a mandrel with an interferencefit and machining an outer surface of the oxidizing inner surfacealuminum tube to a desired diameter and finish; and, oxidizing the outersurface of the oxidized inner surface aluminum tube to produce thealuminum core having an oxidized inner surface and an oxidized outersurface.

The invention further provides an improvement in a method for producinga metallic core for use in blanket cylinder or an image cylinder for usein an electrophotographic process by producing a metallic tube having aninner diameter, an inner surface, an outer surface and an outerdiameter, the inner diameter being smaller than the outer diameter of amandrel so that the metallic tube can be mounted with an interferencefit over the outer diameter of the mandrel and positioning the metallictube on a mandrel with an interference fit and machining an outersurface of the metallic tube to a desired diameter and finish; theimprovement comprising oxidizing the inner surface of the metallic tubeprior to positioning the metallic tube on the mandrel.

The invention also provides an improvement in a method for producing analuminum core for use in a blanket cylinder or an image cylinder for usein an electrophotographic process by producing an aluminum tube havingan inner diameter, an inner surface, an outer surface and an outerdiameter, the inner diameter being smaller than an outer diameter of amandrel so that the aluminum tube can be mounted with an interferencefit over the outer diameter of the mandrel and positioning the aluminumtube on a mandrel with an interference fit and machining an outersurface of the aluminum tube to a desired diameter and finish; theimprovement comprising oxidizing the inner surface of the aluminum tubeprior to positioning the aluminum tube on the mandrel.

The invention provides an image cylinder for an electrophotograpicprocess comprising: a metallic core having at least one of its inner andits outer surfaces oxidized; and, at least one layer of a photosensitiveimage-accepting layer around the outside of the outer surface of themetallic core. Blanket cylinders may also be produced comprising thecores of the present invention and a layer of image-transferringmaterial around the outside of the core.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a metal core according to thepresent invention;

FIG. 2 is a cross-sectional view of a sleeve for an image cylinder or ablanket cylinder, including a metal core according to the presentinvention; and,

FIG. 3 is a cross-sectional end view of the sleeve shown in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the description of the Figures, the same numbers will be used torefer to the same or similar components. Further, additional componentsnecessary for the operation of electrophotographic processes have notbeen shown since their description is not necessary to the descriptionof the present invention.

FIG. 1 shows a cross-section of a metal core 10 for a blanket sleeve oran image cylinder sleeve. The core 10 includes a wall 12 having anoutside 14, an inside 16 and a central axis 18. The core length is shownby the numeral 20. The outer diameter, designated by numeral 26, of thesleeve 22 must be uniform as discussed below.

In FIG. 2, a cylinder sleeve is shown. The cylinder sleeve includeselectrophotographic layers 24 around the metal core 10. The outerdiameter 26 of the sleeve 22 is selected to produce a sleeve of thedesired outer diameter 26′ when the electrophotographic layers arepositioned around the outside of core 10. The outer diameter of thecylinder 30 is shown by the numeral 26′, and as indicated previouslymust have a variation along the length 20 of the sleeve of no more than+/−12.5 microns. The layers deposited on the outside of the core may beas varied as a smoothing layer containing a high concentration of metaloxides, a barrier layer, a charge generation layer, and optionallyadditional layers. Such electrophotographic layers are well known tothose skilled in the art and do not constitute a part of the presentinvention.

In FIG. 3, an end view of the cylinder of FIG. 2 is shown.

As discussed above, it has been found that the previously used nickelcores for the production of sleeves for the production of blanketcylinders and image cylinders have proven to be expensive and qualitycontrol has been a problem. In other words, when the cores are producedby plating, it is difficult to avoid the presence of occasional nodules,voids, wrinkles, cracks and other imperfections in the metal cores. Someof these irregularities can be machined away but frequently result inmachining marks that are also unacceptable. In the case of cracks andthe like, the metal core is not usable.

Since the production of nickel cores has been found to be expensive anddifficult on a reliable basis, improved methods have been sought forproducing metal cores. According to one method, metal extrudate seamlessthin walled extrusion and the like have been used. These extrudatesprovide a constant diameter inner surface, which is readily mounted on amandrel by an air step method as known to those skilled in the art foran interference fit. The extrudate is then readily machined to a desiredouter diameter and finish. The extrudate when removed constitutes ametal core suitable for use in the production of the sleeves. Furtherthe metal core, since it is produced on a common mandrel, has a constantinner diameter. Aluminum is a desirable material for this purpose.Unfortunately, aluminum is relatively soft and in some instances hasbeen found to suffer scratching and other surface abrasions as or beforeit is interference mounted on the mandrel. This can result in the lossof sufficient air in the air step mounting procedure to render itdifficult to position the aluminum extrudate or tubing on the mandrel orto remove the finished aluminum core after machining.

Further the aluminum has been found, in some instances, to gall on themandrel. “Galling” refers to the removal of pieces of the aluminumextrudate inner liner that may adhere to the exterior of the mandrel orto abrasion wear resulting from the interference fit. This not onlyrenders the inner diameter of the metal core variable, but also rendersthe outside of the mandrel of variable diameter in some instances. Theseare both undesirable variables and are desirably avoided.

According to the present invention, it has been found that in suchmachining operations, it is beneficial to oxidize the inside of themetal extrudate or tubing. The oxidized surface is harder and morereadily placed on the mandrel by the air step technique. Further, theharder surface on the inside virtually eliminates galling. This is avery desirable improvement. The machining operation is conducted withthe aluminum extrudate or tubing on the mandrel in an interference fitand after the machining operation has been completed the aluminum coreis readily removed or treated in place to oxidize the outer surface ofthe metal core. This results in an outer surface that is not only harderbut which is also relatively dielectric so that a more uniform core isprovided for use in the production of blanket and image cylinders. Aswell known with respect to image cylinders, a smoothing layer may beplaced immediately over the outside of the metal core to provide aconductive layer of relatively uniform conductivity.

Accordingly, placing an oxidized layer on the inside of the aluminumextrudate tubing or the like greatly facilitates the production of themetal core. Similarly, the positioning of the oxidized coating on theexterior of the core also provides a very desirable improvement. By themethod of the present invention, not only are aluminum cores morereadily produced but other metal cores are also readily produced.Desirably, these metals are selected from the group consisting ofaluminum, nickel, chromium, copper, and rhodium. These materials may beused as tubes, extrudates and the like, which are suitable startingmaterial configurations for the production of the metal cores. To theextent that these metals have an oxide state that is harder or has alower coefficient of friction, the improvement of the present inventionis effective.

Accordingly, the metal cores of the present invention are produced byproducing a metallic tube having an inner diameter, an inner surface, anouter surface and an outer diameter, the inner diameter being smallerthan the outer diameter of a mandrel so that the metallic tube can bemounted with an interference fit over the outer diameter of the mandrel;oxidizing the inner surface of the metallic tube to produce a metallicoxide layer on the inner surface of the metallic tube; positioning theoxidized inner surface metallic tube on a mandrel with an interferencefit and machining an outer surface of the oxidized inner surfacemetallic tube to a desired diameter and finish; and, oxidizing the outersurface of the oxidized inner surface metallic tube to produce themetallic core having an oxidized inner surface metallic core and anoxidized outer.

Preferably the metal is aluminum and the oxide coating is an anodizedcoating, a heating-in-oxygen coating or a sputtering process coating.Oxide coatings may be produced by heating in an oxygen atmosphere to atemperature of at least 500° F. for a time sufficient to produce anoxide layer of the desired thickness. Similarly, sputtering processes,as known to those skilled in the art, can be used to coat both theinside and the outside of the metal core. Desirably, the oxide coatingproduced by the sputtering processes is no greater than about 700nanometers.

The practice of the present invention constitutes a significantimprovement over previous methods for producing the metal cores.

By the practice of the present invention, an image cylinder comprising ametallic core having at least one of its inner and its outer surfacesoxidized and at least one layer of a photosensitive image-acceptinglayer around the outside of the outer surface of the metallic core isproduced. This image cylinder can be produced much more economically andof the same quality as produced by previous methods. Blanket cylindersmay also be produced comprising the cores of the present invention and alayer of image-transferring material around the outside of the core.

The outside of the metal core must be sufficiently smooth and of properdiameter to result in the production of a blanket or image cylindersleeve having suitable tolerances. For instance, the image cylinder andblanket cylinder require a variation in diameter from end to end of nomore than about +/−12.5 microns. The size of the cylinders themselvesmay vary from about 2 centimeters to about 400 centimeters, but thevariation in diameter over the length of the cylinder must be preciselycontrolled to these limits. Typically defects in the surface of thesleeve are unacceptable when such defects are of a size typically assmall as 10 microns in cross-section and 3 microns in depth. Variousother criteria may be applied depending upon the particular applicationto a particular electrophotographic process.

As indicated above, by the process of the present invention, metaltubing, extrudates, and the like can be readily produced of a desireddiameter for positioning on a mandrel by an interference fit followed bymachining to produce the metal core. As also discussed above, there arecertain drawbacks to use of aluminum and other metals with respect togalling, scratching and the like during the interference mounting anddemounting. These drawbacks are reduced by the use of an oxide layer onthe inside, outside, or both, of the metal core to reduce scratching andthe like and further by producing a dielectric core on the outside ofthe metal core. These advantages are readily achieved by oxidizing thesurface of the metal sleeve as discussed above. Desirably, the sleeve isoxidized on its inner surface prior to mounting on the mandrel with theouter surface being oxidized after machining to produce the core. Whileparticular desirable results have been achieved using aluminum treatedby anodizing processes, it will be understood that other oxidizingprocesses could be used with aluminum, such as sputtering techniques,heat oxidation and the like and other processes more adapted to otherspecific metals may be used with other suitable metals.

While the present invention has been described by reference to certainof its preferred embodiments, it is pointed out that the embodimentsdescribed are illustrative rather than limiting in nature and that manyvariations and modifications are possible within the scope of thepresent invention. Many such variations and modifications may beconsidered obvious and desirable by those skilled in the art based upona review of the foregoing description of preferred embodiments.

1. An image cylinder for an electrophotograpic process comprising: a) ametallic core having at least one of its inner and its outer surfacesoxidized; and b) at least one layer of a photosensitive image-acceptinglayer around the outside of the outer surface of the metallic core. 2.The image cylinder of claim 1, wherein the image cylinder includes aplurality of layers around the outside of the metallic core.
 3. An imagecylinder for an electrophotograpic process comprising: a) an aluminumcore having at least one of its inner and its outer surfaces oxidized;and b) at least one layer of a photosensitive image-accepting layeraround the outside of the outer surface of the aluminum core.
 4. Theimage cylinder of claim 3, wherein the image cylinder includes aplurality of layers around the outside of the aluminum core.
 5. Ablanket cylinder for an electrophotographic process comprising: a) analuminum core having at least one of its inner and outer surfacesoxidized; and b) at least one layer of an image-transferring materialaround the outside of the outer surface of the aluminum core.